Fig. 2. Events regulated by Hsps in the death receptor mediated or `extrinsic' pathway to apoptosis. Ligation of cell surface death receptors, e.g. Fas and TNFR1, by the appropriate ligand engages multiple intracellular signals leading to caspase activation and cell death or NF-B-mediated survival. Many elements of these pathways are regulated by the activities of Hsps to help maintain cellular survival following death receptor ligation. Hsp-mediated inhibition is indicated (T-bars) and Hsp-mediated potentiation of a signaling pathway is depicted as a direct interaction between the Hsp and its target (+).